Lattice-Gradient Perovskite KTaO₃ Films for an Ultrastable and Low-Dose X-Ray Detector

Conventional indirect X-ray detectors employ scintillating phosphors to convert X-ray photons into photodiode-detectable visible photons, leading to low conversion efficiencies, low spatial resolutions, and optical crosstalk. Consequently, X-ray detectors that directly convert photons into electric signals have long been desired for high-performance medical imaging and industrial inspection. Although emerging hybrid inorganic-organic halide perovskites, such as CH₃ NH₃ PbI₃ and CH₃ NH₃ PbBr₃ , exhibit high sensitivity, they have salient drawbacks including structural instability, ion motion, and the use of toxic Pb. Here, this work reports an ultrastable, low-dose X-ray detector comprising KTaO₃ perovskite films epitaxially grown on a Nb-doped strontium titanate substrate using a low-cost solution method. The detector exhibits a stable photocurrent under high-dose irradiation, high-temperature (200 °C), and aqueous conditions. Moreover, the prototype KTaO₃ -film-based detector exhibits a 150-fold higher sensitivity (3150 µC Gy_air ^-1 cm^-2 ) and 150-fold lower detection limit (<40 nGy_air s^-1 ) than those of commercial α-Se-based direct detectors. Systematic investigations reveal that the high stability of the detector originates from the strong covalent bonds within the KTaO₃ film, whereas the low detection limit is due to a lattice-gradient-driven built-in electric field and the high insulating property of KTaO₃ film. This study unveils a new path toward the fabrication of green, stable, and low-dose X-ray detectors using oxide perovskite films, which have significant application potential in medical imaging and security operations.